FIG. 1 shows an existing bookmark having a plurality of parallel folding lines. The bookmark particularly includes a bookmark body 10 and an adhesive surface 14. The bookmark body 10 includes a protective surface 11; a folding sheet 12 that can be inserted into a book and a bending surface 13 having a plurality of parallel folding lines 15. When in use, the adhesive surface 14 is adhesively attached to the cover of a book, and the folding sheet 12 is inserted into inner pages of the book to mark a page location of reading interest. However, if the viscidity on the adhesive surface 14 is too strong, it will inevitably damage the papers of the book when peeling off the adhesive surface 14 from the book. Consequently, a bookmark can be only used on one book and it is impossible to move the bookmark to another book for reuse. On the other hand, if the viscidity on the adhesive surface 14 is too weak, after several uses, the adhesiveness on the surface 14 will gradually decrease and disappear, thus causing the bookmark losing its utility and shortening the using life of the bookmark.